Transmucosal Solid Lipid Nanoparticles to Improve Genistein Absorption via Intestinal Lymphatic Transport

Abstract

Genistein (GEN) is a soy-derived isoflavone that exhibits several biological effects, such as neuroprotective activity and the prevention of several types of cancer and cardiovascular disease. However, due to its poor water solubility and the extensive first-pass metabolism, the oral bioavailability of GEN is limited. In this work, solid lipid nanoparticles (SLN) were developed to preferentially reach the intestinal lymphatic vessels, avoiding the first-pass metabolism of GEN. GEN-loaded SLN were obtained by a hot homogenization process, and the formulation parameters were chosen based on already formulated studies. The nanoparticles were characterized, and the preliminary in vitro chylomicron formation was evaluated. The cell uptake of selected nanocarriers was studied on the Caco-2 cell line and intestinal mucosa. The SLN, characterized by a spherical shape, showed an average diameter (about 280 nm) suitable for an intestinal lymphatic uptake, good stability during the testing time, and high drug loading capacity. Furthermore, the intestinal mucosa and Caco-2 cells were found to uptake SLN. The approximately two-fold increase in particle size suggested a possible interaction between SLN and the lipid components of chylomicrons like phospholipid; therefore, the results may support the potential for these SLN to improve oral GEN bioavailability via intestinal lymphatic absorption.

Keywords: genistein; intestinal lymphatic absorption; oral bioavailability; solid lipid nanoparticles.

Figure 1

Particle size and PDI of loaded and unloaded SLN. PDI, p < 0.05: *= B-SLNc vs G-SLNa. Results are reported as mean ± standard deviation (SD).

Figure 2

Physical stability of unloaded and GEN-loaded SLN after 30 days. p < 0.05: *B-SLNc at 0 days vs B-SLNc at 30 days; ^#G-SLNb at 0 days vs G-SLNb at 30 days; ^§ G-SLNa at 0 days vs G-SLNa at 30 days.

Figure 3

TEM image of B-SLNc (a) and G-SLNb (b). (a) Magnification 39000; scale bar 150 nm; (b) magnification 15500, scale bar 300 nm.

Figure 4

In vitro GEN release profile from G-SLNb and the dissolution profile of GEN. Data are reported as mean ± SD (n = 3).

Figure 5

TEM image of the sample obtained from Test 1 (a) and Test 2 (b) (magnification 39,000, scale bar 150 nm).

Figure 6

Histological evaluation of intestinal tissue at time zero: moderate, diffuse chronic lymphoplasmacellular and eosinophilic enteritis. HE; bar: 50 µm.

Figure 7

Histological evaluation of intestinal tissue stored at 25°C at 1 h (A), 2 h (B) and 3 h (C). HE; bar: 50 µm.

Figure 8

Histological evaluation of intestinal tissue stored at 37°C at 1 h (A), 2 h (B) and 3 h (C). HE; bar: 50 µm.

Figure 9

Ex vivo permeation test on intestinal tissue after 1 h: untreated intestinal mucosa, intestinal mucosa treated with free fluorescein solution, and intestinal mucosa treated with F-SLN. Signal (green) / Hoechst 33342 nuclei (blue). Bar: 50 µm.

Figure 10

Ex vivo permeation test on intestinal tissue after 2 h: untreated intestinal mucosa, intestinal mucosa treated with free fluorescein solution, intestinal mucosa treated with F-SLN. Signals (green) / Hoechst 33342 nuclei (blue). Bar: 50 µm.

Figure 11

Effects of in vitro cellular uptake on Caco-2 cells at 30 min (a), 3 h (b), and 24 h (c).